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Nonintegral stoichiometry in CFTR gating revealed by a pore-lining mutation
Cystic fibrosis transmembrane conductance regulator (CFTR) is a unique member of the ATP-binding cassette (ABC) protein superfamily. Unlike most other ABC proteins that function as active transporters, CFTR is an ATP-gated chloride channel. The opening of CFTR’s gate is associated with ATP-induced d...
Autores principales: | , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
The Rockefeller University Press
2012
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3457689/ https://www.ncbi.nlm.nih.gov/pubmed/22966014 http://dx.doi.org/10.1085/jgp.201210834 |
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author | Jih, Kang-Yang Sohma, Yoshiro Hwang, Tzyh-Chang |
author_facet | Jih, Kang-Yang Sohma, Yoshiro Hwang, Tzyh-Chang |
author_sort | Jih, Kang-Yang |
collection | PubMed |
description | Cystic fibrosis transmembrane conductance regulator (CFTR) is a unique member of the ATP-binding cassette (ABC) protein superfamily. Unlike most other ABC proteins that function as active transporters, CFTR is an ATP-gated chloride channel. The opening of CFTR’s gate is associated with ATP-induced dimerization of its two nucleotide-binding domains (NBD1 and NBD2), whereas gate closure is facilitated by ATP hydrolysis-triggered partial separation of the NBDs. This generally held theme of CFTR gating—a strict coupling between the ATP hydrolysis cycle and the gating cycle—is put to the test by our recent finding of a short-lived, post-hydrolytic state that can bind ATP and reenter the ATP-induced original open state. We accidentally found a mutant CFTR channel that exhibits two distinct open conductance states, the smaller O1 state and the larger O2 state. In the presence of ATP, the transition between the two states follows a preferred O1→O2 order, a telltale sign of a violation of microscopic reversibility, hence demanding an external energy input likely from ATP hydrolysis, as such preferred gating transition was abolished in a hydrolysis-deficient mutant. Interestingly, we also observed a considerable amount of opening events that contain more than one O1→O2 transition, indicating that more than one ATP molecule may be hydrolyzed within an opening burst. We thus conclude a nonintegral stoichiometry between the gating cycle and ATP consumption. Our results lead to a six-state gating model conforming to the classical allosteric mechanism: both NBDs and transmembrane domains hold a certain degree of autonomy, whereas the conformational change in one domain will facilitate the conformational change in the other domain. |
format | Online Article Text |
id | pubmed-3457689 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2012 |
publisher | The Rockefeller University Press |
record_format | MEDLINE/PubMed |
spelling | pubmed-34576892013-04-01 Nonintegral stoichiometry in CFTR gating revealed by a pore-lining mutation Jih, Kang-Yang Sohma, Yoshiro Hwang, Tzyh-Chang J Gen Physiol Article Cystic fibrosis transmembrane conductance regulator (CFTR) is a unique member of the ATP-binding cassette (ABC) protein superfamily. Unlike most other ABC proteins that function as active transporters, CFTR is an ATP-gated chloride channel. The opening of CFTR’s gate is associated with ATP-induced dimerization of its two nucleotide-binding domains (NBD1 and NBD2), whereas gate closure is facilitated by ATP hydrolysis-triggered partial separation of the NBDs. This generally held theme of CFTR gating—a strict coupling between the ATP hydrolysis cycle and the gating cycle—is put to the test by our recent finding of a short-lived, post-hydrolytic state that can bind ATP and reenter the ATP-induced original open state. We accidentally found a mutant CFTR channel that exhibits two distinct open conductance states, the smaller O1 state and the larger O2 state. In the presence of ATP, the transition between the two states follows a preferred O1→O2 order, a telltale sign of a violation of microscopic reversibility, hence demanding an external energy input likely from ATP hydrolysis, as such preferred gating transition was abolished in a hydrolysis-deficient mutant. Interestingly, we also observed a considerable amount of opening events that contain more than one O1→O2 transition, indicating that more than one ATP molecule may be hydrolyzed within an opening burst. We thus conclude a nonintegral stoichiometry between the gating cycle and ATP consumption. Our results lead to a six-state gating model conforming to the classical allosteric mechanism: both NBDs and transmembrane domains hold a certain degree of autonomy, whereas the conformational change in one domain will facilitate the conformational change in the other domain. The Rockefeller University Press 2012-10 /pmc/articles/PMC3457689/ /pubmed/22966014 http://dx.doi.org/10.1085/jgp.201210834 Text en © 2012 Jih et al. This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 3.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/3.0/). |
spellingShingle | Article Jih, Kang-Yang Sohma, Yoshiro Hwang, Tzyh-Chang Nonintegral stoichiometry in CFTR gating revealed by a pore-lining mutation |
title | Nonintegral stoichiometry in CFTR gating revealed by a pore-lining mutation |
title_full | Nonintegral stoichiometry in CFTR gating revealed by a pore-lining mutation |
title_fullStr | Nonintegral stoichiometry in CFTR gating revealed by a pore-lining mutation |
title_full_unstemmed | Nonintegral stoichiometry in CFTR gating revealed by a pore-lining mutation |
title_short | Nonintegral stoichiometry in CFTR gating revealed by a pore-lining mutation |
title_sort | nonintegral stoichiometry in cftr gating revealed by a pore-lining mutation |
topic | Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3457689/ https://www.ncbi.nlm.nih.gov/pubmed/22966014 http://dx.doi.org/10.1085/jgp.201210834 |
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